This invention relates to the display of weather or other shaded patterns on a cathode-ray tube. More particularly, it relates to apparatus for widening an electron beam of a cathode-ray tube in order to fill in the area between raster lines generated by a random access cursive display from data stored in a refresh memory permitting use of far fewer raster lines than in conventional raster displays.
The display of weather data on synthetic digital situation displays used for air traffic control and tactical military command and control is a valuable feature. The weather phenomenon typically covers one or more areas of the display and has one or more levels of intensity. Weather data describing a phenomenon (e.g., precipitation) is frequently derived from the same sensor as used for surveillance such as a primary radar; however, it may also be derived from a separate sensor(s) used specifically for weather detection and superimposed on the situation display. The problem addressed by this invention is the presentation of weather data on a random access, cursive (stroke) display in a form that is natural, unambiguous and consistent with the limitations of cursive display generation.
In current cursive display systems, the weather data is digitized and displayed as a series of contour lines and symbols, or hatch lines (radial or rectilinear) and symbols covering the weather area. This data is easily confused with and sometimes obscures other displayed data such as map lines, target symbology and radar data, particularly on a monochrome display. In earlier analog PPI displays, weather information is available in the broadband video signal and is displayed as clutter areas. Similarly on TV raster based display systems, weather is displayed as solid or filled-in areas of "clutter". Variations in weather are represented by intensity or color variations. This filled-in or continuous effect method for displaying weather is desirable based on human factors considerations relating to perception of the weather relative to other data on the display.